Hybrid reflection hologram

ABSTRACT

Hybrid white-light viewable holograms and methods for making them. The holograms are hybrid reflection holograms made using the diffractive structures or gratings of a holographic object such as a transmission hologram or holographic optical element (HOE). The wavefronts of the diffractive structures are converted into a reflection hologram by scanning them with a coherent light source having a profiled narrow beam. The hybrid reflection hologram can exhibit display parameters including the multiple colors, solidity, and color stability of white light reflection holograms, the diffractive color shifting of a white light transmission hologram, three dimensional imaging and a wide variety of dynamic changes. Different areas or images with each of these effects can be combined in a single hologram. These hybrid reflection holograms are ideal for security and forgery prevention applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 13/284,766, entitled “Hybrid Reflection Hologram”,filed on Oct. 28, 2011 and issuing on Jul. 9, 2013 as U.S. Pat. No.8,482,830, which application is a divisional application of U.S. patentapplication Ser. No. 11/688,174, entitled “Hybrid Reflection Hologram”,filed on Mar. 19, 2007, which application claims the benefit of thefiling of U.S. Provisional Patent Application Ser. No. 60/783,502,entitled “Method and Apparatus for Mass Production of Volume Hologramsfrom Plane Holograms”, filed on Mar. 17, 2006, and which application isalso a continuation-in-part application of U.S. patent application Ser.No. 11/459,821, entitled “Method and Apparatus for Mass Production ofHolograms”, filed on Jul. 25, 2006, and issued as U.S. Pat. No.7,616,363 on Nov. 10, 2009, which application claims the benefit of thefiling of U.S. Provisional Patent Application Ser. No. 60/702,785,entitled “Method and Apparatus for Mass Production of ReflectionHolograms and Volume Holographic Optical Elements”, filed on Jul. 26,2005. The specifications and claims of these patent applications areincorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention (Technical Field)

The present invention is a method and apparatus for making a reflectionhologram (or volume hologram) that is made using a transmission hologram(or plane hologram) as the object. This invention obtains the benefitsof the transmission hologram's diffraction spectral color playback andcolor separation of a white light or other multi-wavelength source bydirectly converting the transmission hologram to a reflection hologramfor security and forgery prevention. The present invention preferablyutilizes a single color laser, or optionally a tunable laser or othercoherence light source, to record the hologram by scanning the planehologram with a profiled narrow beam. The resulting hybrid reflectionhologram, when illuminated by white light, can replay in a single coloror in the multiplicity of colors of the original transmission hologramwhile adding the unique optical characteristics of the reflectionhologram.

Background Art

Note that the following discussion refers to a number of publicationsand references. Discussion of such publications herein is given for morecomplete background of the scientific principles and is not to beconstrued as an admission that such publications are prior art forpatentability determination purposes.

Differentiation of Transmission and Reflection Holograms

When constructing a hologram, as the angle difference between the objectbeam (or the wavefronts bouncing off the object) and the reference beamchanges, so does the spacing of the patterns in the emulsion. As long asthe angle difference remains less than about 90 degrees the hologram istypically called a transmission hologram, where “plane” typically meansthat the holographic information is primarily contained in thetwo-dimensional plane of the emulsion. Although the emulsion does have athickness, typically around seven microns, the spacing between fringesis large enough, when the angle is less than about 90 degrees, so thatthe depth of the emulsion isn't being utilized in the recording of thehologram. At about 90 degrees, which is really a convenient butarbitrary point, the angle is great enough, and fringe spacing hasbecome small enough, so that the recording process is taking placethroughout the volume of the thickness of the emulsion, thus producing areflection hologram. Thus the same emulsion can be used to make bothtransmission and reflection holograms depending on the angle differencebetween the reference and object beams. (However, some emulsions orother photosensitive materials are better for either transmissionholograms or reflection holograms.) Thus, as the incidence angle of thereference beam is rotated, either a transmission or reflection hologramis constructed, as shown in FIG. 1.

A very important point for differentiation occurs as the reference beamswings around its arc of possible positions. In a plane (transmission)hologram the reference beam is hitting the film from the same side asthe object beam. In a volume (reflection) hologram the reference beamhits the film from the side opposite to the modulated object beam. Whena difference of 180 degrees is reached, an in-line, volume reflectionhologram is constructed.

A transmission type hologram means that the reference beam must betransmitted through the hologram, in order to decode the interferencepatterns and render the reconstructed image. The light which is used forplayback of a transmission hologram must be coherent or semi-coherent orthe image will not be sharp. If a non-coherent source is used, such asthe light from a common, unfiltered slide projector, then the hologramwill diffract all the different wavelengths. The interference pattern orgrating etched in the emulsion is not particular as to which wavelengthsit bends or focuses; therefore, the result is an unclear overlappingspectrum of colors which somewhat resemble the object. A hologram willplayback just as well with laser light of a different color orwavelength than the light with which it was made. However, the objectwill appear to be of a different size and/or distance from the plate.For example, a hologram of an object made with red light will playbackthat object smaller or seemingly further away if a blue colored laser isused to view it. This is because the grating will bend the blue orshorter light less severely than the red with which it was made and withwhich it is intended to be decoded.

Unlike a transmission hologram, also called a thin, transmission,laser-illuminated, or phase hologram, which requires a coherent orhighly filtered playback source, a reflection hologram, also called avolume or thick hologram, can be viewed very satisfactorily in whitelight or light which contains many different wavelengths. For bestresults, the light preferably should be from a point source and havelimited divergence, such as light from a slide projector light orpenlight, or the sun on a clear day. Any ambient light may alternativelybe used, but this will typically produce lesser quality of the playbackimage. This ability to use white light occurs because, in a way, areflection hologram acts as its own filter. In a reflection hologram thefringes are packed so closely together that they constitute layersthroughout the thickness of the emulsion. The spacing between fringesremains constant. If the distance between fringes is two microns, forexample, then the distance between the remaining layers of fringes willalso be two microns. This distance is a function of the wavelength oflight used in constructing the hologram and also the angle differencebetween reference and object beam. This layered structure allows thereflection hologram to absorb, i.e. not reflect, any of the colors oflight which do not have the correct wavelength. The wavelength whichmatches the fringe spacing will be reflected: the crests of thewavelengths which are too short or too long will eventually miss one ofthe planes and be absorbed into the darkness of the emulsion.

In a reflection type hologram the playback light or reconstruction beamcomes from the same side of the hologram as the viewer. Some parts ofthe incident light are reflected, some are not, depending on theinterference pattern. If the hologram was made correctly the resultshould be a visible three dimensional image. In contrast, fortransmission holograms the reconstruction beam must pass through thehologram and come towards the viewer from the opposite side of thehologram. Just as very few transmission holograms are made in-line (orat 0 degrees), very few reflection holograms are made inline; otherwisethe viewer would have to hold the playback light source close to his orher eyes. Most reflection holograms are made at a less severe angle,perhaps 160 degrees, so that the light can come in at an angle withoutbeing blocked by the person who is trying to see the hologram.

Real and Virtual Images

The image produced by the hologram can either appear to be in front ofthe holographic plate or film, or behind the film (or any position inbetween). As shown in FIG. 2, in the former case it is called a realimage (projection); the latter is called a virtual image. In general itis easier to view a virtual image because you can see through thehologram as if it were a window. Note that the size of the window doesnot affect the apparent size of the image; a smaller window would simplyallow a more confined view, or fewer possible angles of view, of theimage. To view a virtual image the viewer looks through the hologram toperceive the object floating in the space behind it. In contrast, a realimage appears in free space in front of the hologram. It is a littlemore difficult to view a real image because the viewer must find theimage and focus his or her eyes in front of the hologram; the hologramitself is typically less capable to act as a guide for the viewer'seyes.

The real image is very exciting but there are a number of drawbacks. Theobject holographed should be quite a bit smaller than the size of thefilm you are using, or the viewer will not be able to see the completereal image of the object all at once. Also, without special precautionstaken when constructing the hologram, the real image will bepseudoscopic. This means that everything that was closer to the filmwhen the hologram was made will now be further away, and vice versa.This includes both individual objects in a shot or the different planesof space of an individual object. The pseudoscopic image is made byreversing the direction of the reference beam, or by turning thecompleted hologram around until seeing the image in front of the plate.

For example, referring to FIG. 3, if in making a hologram a salt shakeris placed closer to the film than a pepper shaker (the salt shaker mayeven cast a shadow from the object beam onto the pepper shaker), then ina pseudoscopic playback as a real image the pepper shaker will appear tobe closer to the viewer than the salt shaker, which may no longerappear. However, in a virtual image of the same hologram the shakerswould resume their original positions.

Image Plane holograms

Image plane holograms are transmission holograms which are viewable inwhite light and made using a first, master hologram as the object formaking a final, second transmission hologram. However, although themaster hologram is reproduced using an open aperture, the image isachromatic (black and white), and this method can only produce extremelyshallow holograms without substantial blurriness. Rainbow or Bentonholograms are modified image plane holograms in which the finaltransmission hologram is produced using a limited aperture. This reducesblurring of deeper holograms. However, Benton holograms may only beviewed from a small angular range due to the limited aperture; theentire hologram cannot be viewed from, for example, above or below.Because a Benton hologram is a transmission hologram, color control islimited. That is, all of the colors in a Benton hologram will shiftthroughout the color spectrum of the viewing light source, for examplewhite light, when the viewing angle changes.

SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION)

The present invention is a method for producing a reflection hologram,the method comprising the steps of providing an object hologram,disposing the object hologram proximate to a photosensitive material,scanning the object hologram with light from a coherent light source,the light passing through the photosensitive material; and reflectingthe light back through the photosensitive material, thereby forming areflection hologram viewable in white light. The scanning steppreferably comprises scanning a laser beam having a beam thicknesssubstantially less than the length of the object hologram. The scanningstep preferably comprises scanning a laser beam having a width greaterthan or equal to the width of the object hologram. The method preferablyfurther comprises the step of metallizing the front surface of theobject hologram, the rear surface of the object hologram, or a supportfor the object hologram, in which case the reflecting step preferablycomprises reflecting the light from the metallized front surface of theobject hologram, or optionally passing the light through the objecthologram, reflecting the light from the metallized back surface of thehologram or the metallized support, and passing the reflected light backthrough the object hologram.

The method preferably further comprises exposing different hologramareas of the object hologram with different apertures. One of theapertures is optionally open. The method preferably further comprisesselecting a color of a hologram area by modifying the aperture. Thescanning step preferably comprises scanning the light at an angle ofincidence selected from the group consisting of approximately areference angle used to manufacture the object hologram, approximatelyBrewster's angle, approximately the appropriate playback angle toproduce an orthoscopic view, approximately perpendicular to the objecthologram, and between approximately zero and approximately five degrees.The reflection hologram produced preferably comprises an edge litreflection hologram when the angle of incidence is between approximatelyzero and approximately five degrees. The steps of the method mayoptionally be repeated for one or more additional object holograms.

The present invention is also a reflection hologram comprising one ormore hologram areas which exhibit color shifting as a viewing angle ischanged when viewed in light comprising a plurality of wavelengths. Therange of colors exhibited during color shifting preferably comprisesonly a subset of the plurality of wavelengths. The size of the subset ispreferably substantially smaller than a number of the wavelengths. Theplurality of wavelengths preferably comprises a continuous range ofwavelengths. The reflection hologram preferably further comprises atleast one hologram area which does not exhibit color shifting as aviewing angle is changed when viewed in light comprising a range ofwavelengths. Such area preferably comprises a plurality of solid colors.The reflection hologram is preferably lit from the front of the hologramwith white light. The reflection hologram optionally comprises ananti-counterfeiting label. The reflection hologram optionally comprisesa plurality of images which are viewable from a plurality of viewingangles. At least one particular image is preferably viewable only from apredetermined viewing angle. Alternatively, stored information ispreferably accessible only from a predetermined angle. The reflectionhologram optionally comprises an edge lit reflection hologram.

An object of the present invention is to produce a reflection hologramviewable in white light which has the desirable characteristics, such asdiffraction spectrum color shifting control, access to one or morecolors of the full spectrum (including the ability to choose a singlecolor and view it as the non-diffracting color), and control of positionand solidity, of a transmission or similar hologram or holographicoptical element.

An advantage of the present invention is that the diffraction colorspectrum of a transmission hologram, such as a ‘Benton’ limited aperturewhite light transmission hologram, can be converted into a white lightreflection hologram using either a single wave length laser (or othercoherent light source) or tunable wavelength laser (or multiple singlewavelength lasers) without the limitations of lack of color selection ofobjects typically involved in normal white light transmission holograms,and with an aperture that may be opened to any desired value.

Another advantage of the present invention is that multiple colors areachievable without using a mutable laser or without having to swell theemulsion between exposures.

Other objects, advantages and novel features, and further scope ofapplicability of the present invention will be set forth in part in thedetailed description to follow, taken in conjunction with theaccompanying drawings, and in part will become apparent to those skilledin the art upon examination of the following, or may be learned bypractice of the invention. The objects and advantages of the inventionmay be realized and attained by means of the instrumentalities andcombinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and form a partof the specification, illustrate several embodiments of the presentinvention and, together with the description, serve to explain theprinciples of the invention. The drawings are only for the purpose ofillustrating a preferred embodiment of the invention and are not to beconstrued as limiting the invention. In the drawings:

FIG. 1 shows possible reference beam angles when constructing ahologram;

FIG. 2 shows the difference between a real image and a virtual image;

FIG. 3 illustrates a pseudoscopic image;

FIG. 4 depicts a method of making the white-light holograms of thepresent invention wherein the angle of incidence is less than ninetydegrees;

FIG. 5 depicts a method of making the white-light holograms of thepresent invention wherein the angle of incidence is approximately ninetydegrees; and

FIG. 6 depicts a method of making the white-light holograms of thepresent invention wherein the angle of incidence is approximately zerodegrees, thereby producing an edge lit reflection hologram.

DESCRIPTION OF THE PREFERRED EMBODIMENTS (BEST MODES FOR CARRYING OUTTHE INVENTION)

The present invention preferably uses a transmission hologram or otherholographic object, for example, as the object for making a reflectionhologram. Single beam scanning reflection techniques are preferred butother techniques may be used. The mass production methods disclosed inU.S. patent application Ser. No. 11/459,821, entitled “Method andApparatus for Mass Production of Holograms” and incorporated herein byreference, may be used in producing the holograms of the presentinvention.

As used throughout the specification and claims, “reflection hologram”means a volume hologram, reflection hologram, or thick hologram, and thelike. As used throughout the specification and claims, “object hologram”means a transmission hologram, plane hologram, thin hologram,laser-illuminated or laser-lit hologram, phase hologram, holographicoptical element (HOE), Benton hologram, rainbow hologram, image planehologram, limited aperture hologram, transmission type optical reliefhologram, image planed transmission hologram, holographic stereogram,diffractive hologram, diffraction grating, grating structure, multiplexhologram, dot matrix, rainbow, phase, or relief diffraction grating,electron beam hologram, Kinegram, or anything derived from a masterhologram, whether comprising an image or designed for informationstorage and playback, and the like, including but not limited to anyhologram that would be better, or more effectively made, as atransmission hologram, but that would be improved if it could befunctionally converted to a reflection hologram.

As used throughout the specification and claims, “hologram area” meansan area of a hologram or an image or part of an image that is reproducedin a hologram. As used throughout the specification and claims, “whitelight” means white light or any light which comprises multiplewavelengths.

Referring to FIG. 4, the object hologram is placed in the position to beconverted with its exposed emulsion either up or down in relation to thefilm; preferably the emulsion is up and contacts the medium, which ispreferably disposed emulsion side down. Any photosensitive,photoprofilable, or ablatable recording medium may be used in place ofthe film. If the object hologram's exposed emulsion does not contact thefilm, it is preferable to use a larger scanning length, or “thickness”,of the scanned beam. The recording medium can be disposed on anysuitable substrate or carrier medium, including but not limited to glassor film. Thus the photosensitive material is preferably sandwichedbetween the transmission hologram and the glass or film substrate. Acover plate which is clear, or substantially transparent to the laser'swavelength, may optionally be used. The entire “sandwich” is preferablydisposed on a base plate, or optionally a roller or other curvedsupport, the surface of which may optionally be mirrored to enhancereflectivity. The object hologram may also (or alternatively) comprise ahighly reflective metal, typically vacuum-deposited, for example on thegrating surface, or otherwise metallized surface for enhancedreflectivity. Any highly reflective material, such as aluminum, may beused. The hologram or support may alternatively be electroformed, as isnormally done to produce a nickel shim. Any method that will maximizethe reflective qualities of the hologram or support may be used. The“sandwich” is then scanned or exposed with a beam from a source ofcoherent electromagnetic radiation, for example a laser or other light,to a proper exposure time for the photosensitive material being used.The beam passes through the optional cover plate and unexposed recordingmedium and reflects off the base plate or object hologram and backthrough the recording medium to form a reflection hologram. Thethickness or scanning length of the scanning beam is preferably asnarrow as possible, and should be narrower than the length of the objecthologram being scanned. As is shown in the figures, the width of thescanning beam preferably is at least as wide as the width of the objecthologram to be scanned. After the exposure of the copy plate, areflection hologram is developed. The resulting hologram will be areflection hologram but will behave like a transmission hologram incertain aspects and as a reflection hologram in others.

The laser may be scanned at an angle of incidence approximately equal tothe original angle used in the manufacture of the object hologram inorder to produce a pseudoscopic image. Or the angle of incidence may bethe chosen to be the appropriate angle to provide an orthoscopic (i.e.right reading) image, which may enhance the playback diffractionefficiency, preferably in white light, of the finished reflectionhologram. However, it is possible to use any reference angle, or anglebetween the laser beam and the surface of the plate, for the exposure.Some applications may require a different incident angle, for examplewhen reading a predetermined position to obtain selected informationthat is stored in the hologram. If the scan is made at an angle ofincidence different than the reference angle of the master hologram, theoptimal playback viewing angle is typically shifted. For example,Brewster's angle may be used as the scanning angle of incidence, whichsubstantially eliminates any internal reflections of the scanning beam.This substantially eliminates Newton rings which are typically formedwhen the master is made at a different reference angle without having torely on nonreflective coatings.

It is possible to use a zero order, or approximately perpendicular,reference beam, as shown in FIG. 5, which produces particularly goodresults for certain object holograms, for example a dot matrix hologramor holographic image, HOE, or grating formed image. Use of zero orderscanning preferably creates a color in the emulsion, related to therecording wavelength, that shifts when viewed in white light. Thisshift, similar to that of optical variable ink, preferably occurs withincertain parameters that are related to the recording wavelength andthickness of the recording medium.

As shown in FIG. 6, the angle of incidence of the scanning beam may bebetween zero and approximately five degrees. This configuration can beused to produce a reflection edge lit hologram of any size. Typical edgelit holograms are very large transmission holograms for displays. Edgelit reflection holograms made according to the present invention can beof any size, including small labels.

Because the beam is scanned relative to the object hologram, unliketraditional holography methods, the beam need not be stabilized relativeto the object hologram. This enables the use of a much simplermanufacturing apparatus.

Unlike Benton holograms, the aperture used in the present invention maybe fully open. In that case, the resulting hybrid reflection hologram,made from a full spectrum transmission hologram as the object hologram,will typically have a solid color when viewed in white light (within apredefined area and depth of the hologram). Alternatively, the aperturemay be limited to any desired value, producing a master hologram havinga range of playback colors (which range is typically limited whencompared to the range of colors displayed by a transmission hologram).All aperture widths are preferably controlled when producing the masterhologram as is known in the art. Traditional reflection hologram methodsmust select for color by varying the color of the recording laser(s) orswelling the emulsion between exposures. In addition to those methods,the present invention enables the user to choose which colors aredisplayed by modifying the size or angle of the aperture(s) when makingthe master hologram. And different apertures can be used for exposingdifferent hologram areas according to the present invention, so thatwhen the final hybrid reflection hologram is produced, certain hologramareas can have solid, nonshifting colors (as is typical with areflection hologram) while other hologram areas exhibit color shiftingwhen the viewing angle is varied.

The hybrid reflection holograms of the present invention have manyunique properties. Typical reflection holograms can only play back inthe same color it was produced in, even when illuminated with whitelight. In order to get multiple colors, the emulsion must be swelledbetween multiple exposures, or alternatively a mutable laser andmultiple color-sensitive emulsion must be used (with appropriatelycolored object holograms). Also typical reflection holograms do notexhibit color shifting when the viewing angle is changed. In contrast,the present holograms, when illuminated with white light, copy (forexample) the rainbow effect of a rainbow hologram that was used as theobject hologram. The colors may optionally have been modulated by thecolor of the exposing laser or other known techniques. The holograms ofthe present invention preferably have some of the benefits and playbackproperties of reflection holograms; for example, viewability in areflected white light source, image solidity and stability, colorselection, color stability (limited color shifting), wider deepercolors, front reflection playback, and single area image playback. Theyexhibit some or all of the diffraction colors and visual effects of theoriginal transmission hologram while retaining the color control of areflection hologram. The multiple shifting colors displayed by thehybrid reflection holograms of the present invention are typicallycentered around the reference angle and can change as the viewing angleis shifted, although the range of colors is typically far more limitedthan the range exhibited by a transmission hologram, which, like aprism, displays all of the colors included in the viewing light source(e.g. a complete spectrum for white light). Thus the range of colorshifting that the hybrid reflection hologram exhibits preferablycomprises only a subset of the colors included in the light source.

Unlike transmission holograms (e.g. embossed security holograms or thosemade from diffraction gratings by, for example, dot matrix or e-beammethods), reflection holograms typically can only be viewed fromapproximately the direction and angle of the recording source; theycannot be viewed from the reverse angle. Thus, as a reflection hologram,the present invention can produce another image (which is the same as ordifferent than the original image) that is viewable only from thereverse angle, or other images which are viewable from their ownreference angles. This capability is advantageous for securityapplications. This also is difficult to accomplish cleanly usingtransmission holograms known in the art, since there can be interferenceor “crosstalk” between the multiple images. And, since reflectionholograms are more sensitive to the reference angle for image playbackthan transmission holograms, the hybrid reflection holograms of thepresent invention may be used for applications where precise control ofthe viewing angle, or location of stored information to be transferred,is desired while still providing some of the advantages of transmissionholograms, such as color control and color shifting.

The present invention enables the use of object holograms or HOE's asreflections which do not comprise a reflective backing or metalsurfacing (as is typically needed when producing embossed holograms) orthe need for a back lighting source to playback the hologram in whitelight conditions. Thus the use of front mounted lighting is possible,with all its attendant benefits. Unlike transmission holograms, theinformation is stored throughout the emulsion layer of the hybridreflection hologram of the present invention, as a true reflectionhologram, and can not be electroformed or copied as easily asinformation in a transmission hologram, Benton or rainbow hologram, orthe like. Thus holograms of the present invention are more secure thantransmission holograms and thus more suitable for use as OpticallyVariable Devices, which are used, for example, as anti-counterfeitinglabels. In addition, the quality and diffraction efficiency of theholograms produced according to the present invention is high enough tomeet production standards for commercial use, usingcommercially-available recording media.

Multiple object holograms may be used to create a hybrid reflectionhologram according to the present invention by multiply exposing thephotosensitive medium. For example, the photosensitive medium may beexposed at different stations where different object holograms arelocated.

The hybrid reflection hologram of the present invention may optionallybe affixed to a label, such as an RFID tag. The information in the RFIDtag may correspond to information in the hologram. It may alsooptionally comprise printing which may relate to the image or otherinformation contained in the hologram, similar to printing on embossedholograms known in the art.

A reflection hologram according to the present invention may optionallybe made using normal (non-holographic) object. In this case, there wouldbe no color shifting, but if a direct physical developer, for example,were used, the hologram may exhibit chromatic dispersion.

Example 1

A hybrid reflection hologram of the present invention was produced asfollows:

-   -   1. A limited aperture white light transmission hologram of the        size required was made.    -   2. The transmission hologram should be of high diffraction        quality for best results. For this example, certain areas of a        transmission hologram were exposed using a hinge point method        commonly known in the industry to enable the separation of        colors in the finished limited aperture white light hologram. It        may be advantageous to make the color slits as narrow as        possible in order to maximize the diffractive color range of the        finished white light transmission hologram. Additional areas of        the hologram were exposed using an open aperture and then were        combined with the areas previously exposed.    -   3. A photosensitive photoresist, commonly used in embossed        holography, was used as the recording medium. The hologram was        developed in the normal manner.    -   4. When the hologram was finished it was metallized with        aluminum, directly onto the surface gratings.    -   5. The metallized object hologram was placed in the position to        be scanned and converted to a hybrid reflection hologram.    -   6. In suitable conditions (e.g. under safe lighting if required)        the holographic emulsion was placed in contact with the        metallized surface of the transmission hologram, forming a        “sandwich” structure. The grating structures were in contact        with the photosensitive material.    -   7. Relative to the angle that was used for the making of the        original limited aperture transmission hologram, the object        hologram was evenly scanned at an appropriate angle of incidence        for playback with a single beam of a laser.    -   8. The photosensitive material was exposed at the correct        exposure for the photosensitive material being used.    -   9. GP8, a Russian developer commonly used to make reflection        holograms, was used to develop the hologram. A fixing agent was        subsequently used. (Use of a fixing agent is optional.)    -   10. After washing and drying, the hologram was viewed in white        light.

Although the invention has been described in detail with particularreference to these preferred embodiments, other embodiments can achievethe same results. Variations and modifications of the present inventionwill be obvious to those skilled in the art and it is intended to coverall such modifications and equivalents. The entire disclosures of allpatents and publications cited above are hereby incorporated byreference.

What is claimed is:
 1. A reflection hologram comprising one or morehologram areas which exhibit controlled color changes that shift orchange to a different color as a viewing angle is changed when viewed inwhite light comprising a plurality of wavelengths, at least onenon-stereogram hologram area that does not exhibit color shifting as aviewing angle is changed when viewed in light comprising a range ofwavelengths, and information stored throughout an emulsion layer, andwherein said reflection hologram does not comprise a reflective backing.2. The reflection hologram of claim 1 wherein a range of colorsexhibited during color shifting comprises only a subset of the pluralityof wavelengths.
 3. The reflection hologram of claim 2 wherein a size ofthe subset is substantially smaller than a number of the wavelengths. 4.The reflection hologram of claim 1 wherein the plurality of wavelengthscomprises a continuous range of wavelengths.
 5. The reflection hologramof claim 1 wherein said at least one hologram area comprises a singlecolor or a plurality of single colors.
 6. The reflection hologram ofclaim 1 which is lit from the front of the hologram with white light. 7.The reflection hologram of claim 1 comprising an anti-counterfeitinglabel.
 8. The reflection hologram of claim 1 comprising a plurality ofimages which are viewable from a plurality of viewing angles.
 9. Thereflection hologram of claim 8 wherein a particular color is viewableonly from a predetermined viewing angle.
 10. The reflection hologram ofclaim 8 wherein stored color information is accessible only from apredetermined angle.
 11. The reflection hologram of claim 1 comprisingan edge lit reflection hologram.
 12. The reflection hologram of claim 1comprising diffraction spectrum color shifting control.
 13. Thereflection hologram of claim 1 comprising an optically variable device.14. A reflection hologram comprising at least one area exhibiting colorstability or limited color shifting, including one or morenon-stereogram first areas comprising one or more single, nonshiftingcolors and one or more second areas that exhibit controlled colorchanges that shift or change to a different color when a viewing angleis varied when viewed in white light comprising a plurality ofwavelengths, and additionally comprising information stored throughoutan emulsion layer, and wherein said reflection hologram does notcomprise a reflective backing.
 15. The reflection hologram of claim 14comprising colors modulated by a color of an exposing laser.
 16. Thereflection hologram of claim 14 comprising an optically variable device.17. The reflection hologram of claim 14 comprising a plurality of imageswhich are viewable from their own reference angles.
 18. The reflectionhologram of claim 14 comprising information stored by using multipleincident angles during exposure.
 19. The reflection hologram of claim 18comprising a subset of the colors included in an illuminating lightsource.
 20. The reflection hologram of claim 14 attached to aradio-frequency identification (RFID) tag.